The present invention relates to an electric wire, a coil, an apparatus for designing the electric wire, and an electric motor.
In winding wires and power cables of devices to which high-frequency current is applied (transformers, motors, reactors, induction heaters, magnetic head devices, and the like), the magnetic field generated by the high-frequency current causes an eddy current loss within a conductor, and the AC resistance (high-frequency resistance) is therefore increased (or the skin effect and the proximity effect are increased). This causes heat generation and increases power consumption. Countermeasures to prevent the increases in the skin effect and proximity effect include, generally, reducing the diameter of wires and employing litz wires including strands individually coated and insulated (see Japanese Patent Laid-open Publication No. 2009-129550, Japanese Patent Laid-open Publication No. S62-76216, Japanese Patent Laid-open Publication No. 2005-108654, International Publication No. 2006/046358 and Japanese Patent Laid-open Publication No. 2002-150633, for example).
As one of electric wires used for winding wires and the like, for example, copper-clad aluminum wire (hereinafter, referred to as CCA wire) is known. The CCA wire includes aluminum wire (hereinafter, referred to as Al wire) whose surface is covered with a thin copper layer. However, in a particular frequency range in which high-frequency wire is used, it is difficult to make the AC resistance of the high-frequency wire definitely lower than that of copper wire (hereinafter, referred to as Cu wire) having a same diameter as that of the high-frequency wire.